Modular electronic systems are generally configured as a shelf to optimize space efficiency within a central office or other similar facility. Card shelves include individual plug-in electronic module cards having different functions that communicate across a backplane. The electronic cards have different thicknesses depending on the amount of electronic circuitry contained in each electronic card. The electronic cards may also have flanges at the top or bottom which fit into grooves in the card shelf for sliding the electronic cards into the card shelf and plugging the electronic cards into connectors located in the backplane of the card shelf.
The card shelf may also include an open or perforated top and bottom portion to allow thermal energy generated by the electronic cards during operation to escape the card shelf. Additionally, the card shelf may include a fan assembly for directing air flow through the card shelf to dissipate the thermal energy generated by the electronic cards during operation. The fan assemblies include air filters to purify air and remove harmful dust and other contaminants.
Known card shelves present certain drawbacks. For example, to maximize space within a card shelf, electronic cards are placed in close proximity to one another. As a result, dissipation of thermal energy generated by the electronic cards during operation must be closely monitored in order to maintain proper operation of the electronic cards.
Typical fan assemblies and other active cooling systems use a flow sensor to monitor the performance of air filters which can become clogged and reduce the dissipation of thermal energy in the card shelf. Such flow sensors, however, are expensive and inaccurate, frequently generating false alarms that cause excess maintenance, servicing, and down time. In addition, conventional systems are unable to provide diagnosis of problems within the cooling system.